Silicon is well known in the art for providing an effective coating for use with a variety of applications. For example, silicon is often used to coat metals, thereby reducing corrosion of the metal. One of the disadvantages associated with the use of silicon as a coating has been the difficulty of providing silicon in an aqueous medium. This is in part due to silicon being insoluble in water.
However, silicon is soluble in alkalis. Several attempts have been made to combine silicon or other metals in an aqueous solution, to provide a plating bath having a source of silicon or other metals for deposition on a substrate or the like. For example, U.S. Pat. No. 4,571,328 to Rice relates to one such combination. As discussed in U.S. Pat. No. 4,571,328, previous methods for electrolytic deposition were difficult and inefficient since operations at high temperatures or closed, inert atmospheres were often required. Additionally, silicon hydrides were also unexpected in the aqueous form.
While the aqueous electrodeposition baths produced in accordance with U.S. Pat. No. 4,571,328 alleviate many of the problems associated with prior art techniques, the described hydrides are produced according to certain stoichiometric proportions of metal, alkaline metal hydroxide and water. For example, one embodiment teaches the formation of an aqueous hydride from the combination of silicon, sodium hydroxide and water in the ratio of 6:1:10 respectively by mole percent. While the resulting hydrides have proven successful, the manufacturing process is complex due to the desirability of manufacturing according to the specific ratios.
U.S. Pat. No. 4,570,713, also to Rice, relates to aqueous silicon compounds for use with oil recovery methods. As with U.S. Pat. No. 4,571,328, this patent teaches the formation of a metal hydride from reacting a non-alkaline metal with an alkaline metal hydroxide in water. The metal hydride is water-soluble and may be diluted. The solution is then used as a plating bath and electroplated onto a cathode. However, this patent also describes the combination of certain stoichiometric amounts of metal, alkaline metal hydroxide and water in a preselected mole percent to produce the desired metal hydride.
It is also known in the art that polysilicates exhibit polymer characteristics. For example, these compounds are suitable for use as detergents, coatings, to reduce viscosity and pressure differential. Additionally, these compounds act as sequestering agents by maintaining compounds in suspension. They are also suitable for use as surfactants and emulsion agents. However, it is further known in the art that the production of stable polysilicates and the maintenance thereof in solution is difficult. This has been due in part to hydrolysis reactions occurring, causing polysilicates to form ortho silicates which precipitate out of solution and/or exhibit substantially lower detergent characteristics. Consequently, such compounds manufactured in accordance with the prior art techniques have a short shelf life. This is particularly undesirable since ortho silicates do not exhibit the characteristics of polysilicates.
It would therefore be desirable to provide a method of manufacturing aqueous hydrides or polysilicates that are stable in an alkali solution.